This invention relates to an internal combustion engine using poppet type valves to direct gases into and out of one or more cylinders. More particularly, the orientation of a roller lifter follower in a pushrod operated engine is to be kept constant during rotation of a rotatable element to alter the phasing of the valves in the engine.
A description of a phasing system for roller lifter followers on a camshaft is given by Riley in U.S. Pat. No. 6,155,216, which is hereby incorporated by reference for all that is taught and disclosed therein.
As the rotatable element, such as an eccentric sleeve, is rotated to phase the roller lifter follower (hereinafter simply xe2x80x9croller lifterxe2x80x9d), the roller lifter orientation must be controlled to allow the roller to follow the cam lobe on the camshaft. In fixed timing systems a simple pin or plate is usually sufficient to prevent the roller lifter from rotating around its longitudinal axis during operation. The arcuate path of the phased roller lifter requires an extra degree of freedom of movement. Therefore additional measures must be taken in order to maintain controlled orientation of the roller lifter.
The present invention describes a system for providing controlled orientation of a roller lifter in a pushrod engine using a phasing device to change the point of contact of the roller lifter on the cam. This system is applicable to single or multiple roller lifters. It also applies to roller lifters that may have curved surfaces for contacting the cam, but may not have rollers.
Roller lifters usually have either one or more flat surfaces machined into the outer body of the roller lifter. With the phasing mechanism described in U.S. Pat. No. 6,155,216, the arcuate motion of the roller lifter during phasing would result in excessive clearance at most positions if a fixed anti-rotation mechanism were attempted, and misalignment between cam and roller lifter could result. In the present invention the roller lifter is allowed to move along a constraining member of a constraining mechanism, and the constraining mechanism is allowed to move freely in a direction substantially parallel to a line perpendicular to the flat surface machined onto the roller lifter. As the roller lifter moves through its arcuate path, the flat surface(s) of the roller lifter will slide across the constraining member(s) of the constraining mechanism.
An alternative embodiment of this anti-rotation approach is to have locating pins extending from the side of the lifter, perpendicular to the roller lifter longitudinal axis. These locating pins would engage slots in a constraining mechanism and the constraining mechanism would be free to move in a direction substantially perpendicular to both the longitudinal axis of the roller lifter and the axis of the locating pins.
Another alternative embodiment of this anti-rotation approach is to machine one or more slots into the body of the roller lifter parallel to the longitudinal axis of the lifter. Engaging pins may be inserted into these slots, the engaging pins being attached to a constraining mechanism that may move substantially perpendicular to the engaging pins and the longitudinal axis of the lifter.